This application claims Paris Convention priority of DE 101 19 678.4 filed Apr. 20, 2001 the complete disclosure of which is hereby incorporated by reference.
The invention concerns a rotary tampon printing press comprising an engraved roller with vertical axis of rotation, one or more tampon rollers, and an ink dispensing system for supplying ink to the engraved roller.
Rotary tampon printing presses with vertical engraved rollers are known in the art. Uniform application of ink onto the engraved roller such that the engravings are completely filled with printing ink is difficult with these rollers.
To overcome this problem, the present invention proposes that, in a rotary tampon printing press of the above-mentioned type, the ink dispensing system comprise an ink collecting trough, and an Archimedean screw immersed into the ink collecting trough for supplying the printing ink, wherein the Archimedean screw comprises a guiding means which guides the printing ink to the engraved roller.
In the inventive rotary tampon printing press, the printing ink with which the engraved roller is coated is supplied by means of an Archimedean screw from the ink collecting trough and guided via the guiding means to the peripheral surface of the engraved roller thereby supplying ink to the engravings. This system is advantageous in that it operates contact-free, in contrast to systems which use ink dispensing rollers or the like. This system is also independent of the height of the engraved roller since the Archimedean screw can supply the printing ink to any desired height.
A further development provides that the Archimedean screw, the ink trough and the guiding means are parts of the ink dispensing system. This is particularly advantageous in that the ink dispensing system can be handled separately without impairing the engraved roller or the tampon roller. The positions of the engraved roller and the tampon roller must therefore not be altered, in particular, when the printing ink is changed. Maintenance and repair are simplified since the entire ink dispensing system can be replaced.
The guiding means is advantageously formed to join onto the outlet opening of the Archimedean screw and extend to the peripheral surface of the engraved roller. This provides optimum guidance of the printing ink to its destination. In particular, the dosing gap between the guiding means and the peripheral surface of the engraved roller can be adjusted.
The Archimedean screw is preferably vertical. It is also feasible to slightly incline the Archimedean screw, in particular, in the direction of the engraved roller.
A collecting means is provided below the engraved roller for collecting excess printing ink which runs off the engraved roller. This collecting means is fashioned as a collecting trough and has an inclined bottom which feeds into the ink-collecting trough of the ink dispensing system. In this fashion, the printing ink which runs off the engraved roller is returned into the ink dispensing system.
In a particularly preferred embodiment, the Archimedean screw is driven by a speed controlling drive. This permits optimum adjustment of the capacity to the requirements or type of printing ink.
In a further development, the drive comprises a sensor for determining the power input. This sensor adjusts the power of the drive to the changing ambient conditions. Towards this end, a monitoring means is provided which comprises the corresponding control circuits. A supply device is also provided for adding thinning agent when the ink thickness exceeds a threshold value.
Preferably, the guiding means can be adjusted to the height of the engraved roller. As mentioned above, this permits use of the same ink dispensing system for engraved rollers of different heights, e.g. heights of 50 mm, 100 mm etc.
To meet environmental conditions and minimize evaporation of ink components, the system is substantially closed.
To ensure that the printing quality remains constant, the tampon roller is coupled to a residual ink collector. This residual ink collector, formed e.g. as a revolving roller to be pressed onto the tampon, bears an ink-collecting sheet around its periphery which is exchanged when required. It is, of course, also possible to press a sheet band onto the revolving roller of the tampon roller to thereby collect the residual ink.
Further advantages, features and details of the invention can be extracted from the following description which illustrates in detail a particularly preferred embodiment with reference to the drawing. The features shown in the drawing and mentioned in the description and in the claims may be essential to the invention either individually or collectively in any arbitrary combination. In the drawing: